A pulse oximeter is a device that clips onto the tip of a finger. It records the heart rate (pulse rate) in beats per minute and the percentage of oxygen in the blood (%SpO$_2$).
A student used a pulse oximeter to study how exercise affects heart rate and the percentage of oxygen in the blood.
Before exercising, the student took three readings from the pulse oximeter (0, 1 and 2 minutes). They then exercised for five minutes. At the end of five minutes, they took four more readings at one minute intervals (7, 8, 9 and 10 minutes).
Some of the results are shown in Table 2.1.
The photograph in Fig. 2.1 shows the pulse oximeter readings at 1 minute.
(a(i))[1]
Enter the readings for 1 minute into Table 2.1.
(a(ii))[4]
On the grid below, draw a line graph of heart rate against time. Connect the points with ruled straight lines.
(a(iii))[2]
Identify the period of exercise on your graph by drawing two lines.
Draw one starting from the point where exercise began and ending at the axis. Label this line $S$.
Draw one starting from the point where exercise finished and ending at the axis. Label this line $E$.
(a(iv))[2]
Suggest why it would not be valid to use the graph to find the heart rate at 5 minutes.
(b(i))[3]
Describe any changes in heart rate and the percentage of oxygen in the blood during the investigation, using the data in your graph and Table 2.1.
(b(ii))[2]
The student thought that changes in their breathing could have affected the percentage of oxygen in their blood during exercise. Suggest two changes in breathing that could be measured to help explain the percentage oxygen levels during the investigation.
Worked solution & mark scheme
This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: “64 and 98 in the correct columns” …